Death Knights were introduced in the Knights of the Frozen Throne expansion, which was released in August. These powerful cards have been staples in the Hearthstone meta since they were launched, but they've been deemed too powerful for Arena.

"While the Death Knight Hero cards are exciting and powerful to play, their permanent Hero Power upgrades are hard to combat in a format where answers are limited," Zeriyah said.

Zeriyah clarified that Death Knight Hero cards won't be removed from existing drafted Arena decks. Blizzard plans to "continue to monitor Arena balance and make changes on an as-needed basis."

If you're a fan of using Death Knight Hero cards in Arena, you should try to draft them while you still can—because they'll be removed from the mode next Tuesday.